Info Structure and Method Forming Same

ABSTRACT

A method includes encapsulating a package component in an encapsulating material, with the encapsulating material including a portion directly over the package component. The portion of the encapsulating material is patterned to form an opening revealing a conductive feature in the package component. A redistribution line extends into the opening to contact the conductive feature. An electrical connector is formed over and electrically coupling to the conductive feature.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional of U.S. patent application Ser. No.15/939,615, entitled “Info Structure and Method Forming Same,” filed onMar. 29, 2018, which claims the benefit of the following provisionallyfiled U.S. Patent application: Application Ser. No. 62/589,892, filedNov. 22, 2017, and entitled “Low-cost Info Structure and Method FormingSame,” which applications are hereby incorporated herein by reference.

BACKGROUND

With the evolving of semiconductor technologies, semiconductorchips/dies are becoming increasingly smaller. In the meantime, morefunctions need to be integrated into the semiconductor dies.Accordingly, the semiconductor dies need to have increasingly greaternumbers of I/O pads packed into smaller areas, and the density of theI/O pads rises quickly over time. As a result, the packaging of thesemiconductor dies becomes more difficult, which adversely affects theyield of the packaging.

Conventional package technologies can be divided into two categories. Inthe first category, dies on a wafer are packaged before they are sawed.This packaging technology has some advantageous features, such as agreater throughput and a lower cost. Further, less underfill or moldingcompound is needed. However, this packaging technology also suffers fromdrawbacks. Since the sizes of the dies are becoming increasinglysmaller, and the respective packages can only be fan-in type packages,in which the I/O pads of each die are limited to a region directly overthe surface of the respective die, with the limited areas of the dies,the number of the I/O pads is limited due to the limitation of the pitchof the I/O pads. If the pitch of the pads is to be decreased, solderbridges may occur. Additionally, under the fixed ball-size requirement,solder balls must have a certain size, which in turn limits the numberof solder balls that can be packed on the surface of a die.

In the other category of packaging, dies are sawed from wafers beforethey are packaged. An advantageous feature of this packaging technologyis the possibility of forming fan-out packages, which means the I/O padson a die can be redistributed to a greater area than the die, and hencethe number of I/O pads packed on the surfaces of the dies can beincreased. Another advantageous feature of this packaging technology isthat “known-good-dies” are packaged, and defective dies are discarded,and hence cost and effort are not wasted on the defective dies.

In a fan-out package, a device dies is encapsulated in a moldingcompound, which is then planarized to expose the device die. Dielectriclayers are formed over the device dies. Redistribution lines are formedin the dielectric layers to connect to the device die. Seal rings may beformed in the dielectric layers when the redistribution lines areformed. The fan-out package may also include through-vias penetratingthrough the molding compound.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 9 illustrate the cross-sectional views of intermediatestages in the formation of a package including a seal ring penetratingthrough a molding material in accordance with some embodiments.

FIGS. 10 through 21 illustrate the perspective views and cross-sectionalviews of intermediate stages in the formation of a package includingmetal pins penetrating through a molding material in accordance withsome embodiments.

FIGS. 22 through 24 illustrate the magnified views of some portions ofpackages in accordance with some embodiments.

FIGS. 25 and 26 illustrate process flows for forming packages inaccordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A package and the method of forming the same are provided in accordancewith various exemplary embodiments. The intermediate stages of formingthe package are illustrated in accordance with some embodiments. Somevariations of some embodiments are discussed. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements.

FIGS. 1 through 9 illustrate the cross-sectional views of intermediatestages in the formation of a package in accordance with someembodiments. The steps shown in FIG. 1 through 9 are also illustratedschematically in the process flow 500 as shown in FIG. 25.

FIG. 1 illustrates carrier 20 and release layer 22 coated on carrier 20.Carrier 20 may be a glass carrier, a ceramic carrier, or the like.Carrier 20 may have a round top-view shape, and may have a size of asilicon wafer. For example, carrier 20 may have an 8-inch diameter, a12-inch diameter, or the like. Release layer 22 may be formed of aLight-To-Heat-Conversion (LTHC) coating, which may be removed along withcarrier 20 from the overlying structures that will be formed insubsequent steps. In accordance with some embodiments of the presentdisclosure, release layer 22 is formed of an epoxy-based thermal-releasematerial. Release layer 22 may be disposed onto carrier 20 throughcoating and curing.

Dielectric layer 24 (which is sometimes referred to as a base layer forforming the overlying structure or a buffer layer) is formed overrelease layer 22. The bottom surface of dielectric layer 24 may be incontact with the top surface of release layer 22. In accordance withsome embodiments of the present disclosure, dielectric layer 24 isformed of a polymer, which may be a photo-sensitive material such aspolybenzoxazole (PBO), polyimide, or the like. In accordance withalternative embodiments, dielectric layer 24 is formed of anon-photo-sensitive material or an inorganic dielectric material, whichmay be a nitride such as silicon nitride, an oxide such as siliconoxide, Phospho-Silicate glass (PSG), Boro-Silicate Glass (BSG),Boron-Doped Phospho-Silicate Glass (BPSG), or the like.

FIG. 1 also illustrates the placement/attachment of package components28. The respective step is illustrated as step 502 in the process flowshown in FIG. 25. Package components 28 are attached to dielectric layer24 through Die-Attach Films (DAFs) 26, which are adhesive films. Each ofpackage components 28 may include a semiconductor substrate (not shownseparately) having a back surface (the surface facing down) in physicalcontact with the respective underlying DAF 26. Package components 28 mayinclude integrated circuit devices (such as active devices, whichinclude transistors, for example, not shown) at the front surface (thesurface facing up) of the semiconductor substrate. Package components 28may include a logic die such as a Central Processing Unit (CPU) die, aGraphic Processing Unit (GPU) die, a mobile application die, a MicroControl Unit (MCU) die, an input-output (IO) die, a BaseBand (BB) die,an Application processor (AP) die, or the like. Package components 28may also include a memory die such as a Dynamic Random Access Memory(DRAM) die or a Static Random Access Memory (SRAM) die. Packagecomponents 28 may also include System on Chip (SoC) dies, memory stacks(such as High-Bandwidth Memory (HBM) cubes), packages, or the like.Package components 28 may be the same as each other or different fromeach other.

Although two package components 28 are illustrated as an example, theremay be one package component 28 or more than two package components perpackage. It is appreciated that the packaging process may be performedat wafer-level or die-level. When performed at the wafer-level, there isa plurality of identical groups of package components, with each groupbeing illustrated schematically, placed over carrier 20, and theplurality of groups of package components is allocated as an array.

In accordance with some exemplary embodiments, conductive features 30are pre-formed as portions of package components 28, wherein conductivefeatures 30 are electrically coupled to the integrated circuit devicessuch as transistors (not shown) in package components 28. Conductivefeatures 30 may be metal pillars (such as copper pillars), metal pads,micro-bumps, or the like. Although one conductive feature 30 isillustrated for each of package components 28 for simplicity, eachpackage component 28 may include a plurality of conductive features 30.Throughout the description, conductive features 30 are referred to asmetal pillars, although they may be other types of conductive features.

In accordance with some embodiments of the present disclosure, packagecomponents 28 include top dielectric layers 32 filling the gaps betweenneighboring metal pillars 30. Top dielectric layers 32 may includeportions covering at least some portions of the top surfaces of metalpillars 30. In accordance with some embodiments of the presentdisclosure, top dielectric layers 32 are formed of a polymer, which maybe PBO or polyimide. In accordance with some embodiments of the presentdisclosure, dielectric layers 32 are etched to form openings, throughwhich metal pillars 30 are exposed. In accordance with alternativeembodiments of the present disclosure, no openings are formed to exposemetal pillars 30 at this time. Rather, metal pillars 30 are revealed ata time after molding material is formed.

Next, package components 28 are encapsulated by encapsulating material36, as shown in FIG. 2. The respective step is illustrated as step 504in the process flow shown in FIG. 25. Encapsulating material 36 fillsthe gaps between neighboring package components 28. Encapsulatingmaterial 36 may be an epoxy (or resin) based material, and may bephoto-sensitive. Encapsulating material 36 may be formed of a dry film,which is pre-formed as a film and then laminated on the structure shownin FIG. 1. The laminated film may be pressed at an elevated temperature,for example, in the range between about 25 degrees and about 150degrees. The dry film may be formed of epoxy (or resin) capped byPolyethylene (PE) or Polyethylene Terephthalate (PET) protecting film onthe both side, or the like. In accordance with alternative embodiments,encapsulating material 36 is dispensed in a flowable form, and is thencured (through thermal curing or Ultra-Violet (UV) curing, for example).The top surface of encapsulating material 36 is higher than the topsurfaces of package components 28, with package components 28 covered bya thin layer of encapsulating material 36. Furthermore, typical moldingmaterials such as molding compound and underfill may include fillerparticles such as SiO₂, Al₂O₃, or silica particles. In accordance withsome embodiments of the present disclosure, encapsulating material 36 isfree from filler particles, and the entire encapsulating material 36 maybe formed of a homogenous material. Making encapsulating material 36free from filler particles allows the portions of encapsulating material36 directly over package components 28 to be very thin withoutsacrificing the isolation ability.

FIG. 23 schematically illustrates a magnified view of a portion of thestructure shown in FIG. 2. Due to the height of package components 28,the top surface of encapsulating material 36 may include a first portiondirectly over package component 28, and a second portion not directlyover package component 28. The second portion encircles the firstportion. In accordance with some embodiments of the present disclosure,the formation of encapsulating material 36 does not include aplanarization process (such as a Chemical Mechanical Polish (CMP)process or a mechanical grinding process). Accordingly, the firstportion of the top surface of encapsulating material 36 is higher thanthe second portion of the top surface of encapsulating material 36, witha smooth transition from the first portion to the second portion. Theheight difference ΔH1 between the first portion and the second portionmay be greater than about 2 μm, and may be in the range between about 4μm and about 10 μm. In accordance with alternative embodiments of thepresent disclosure, a planarization process is performed, and hence thetop surface of encapsulating material 36 is planar. The portions ofencapsulating material 36 directly over package components 28 may alsohave thickness T1 in the range between about 10 μm and about 30 μm.

Referring to FIG. 3, openings 38A and 38B are formed in encapsulatingmaterial 36. The respective step is illustrated as step 506 in theprocess flow shown in FIG. 25. In accordance with some embodiments ofthe present disclosure, openings 38A penetrate through encapsulatingmaterial 36, so that dielectric layer 24 is exposed. Openings 38B alsopenetrate through encapsulating material 36, so that metal pillars 30are exposed. If metal pillars 30 are still covered by dielectric layer32 at this time, dielectric layer 32 is patterned, for example, in anetching step (which may be performed using the patterned encapsulatingmaterial 36 as the etching mask), until metal pillars 30 are revealed.In accordance with some embodiments of the present disclosure,encapsulating material 36 is formed of a photo-sensitive material, andthe patterning of encapsulating material 36 may be achieved throughlight exposure using a photolithography mask (not shown), which includesopaque portions and transparent portions, and then developingencapsulating material 36 to form openings 38A and 38B. Althoughopenings 38A are illustrated as discrete openings in the cross-sectionalview shown in FIG. 3, in a top view of the structure shown in FIG. 3,the illustrated openings 38A may be portions of an opening ring thatencircles package components 28. Openings 38B, on the other hand, arediscrete openings, with each exposing one of the metal pillars 30.

FIGS. 4 and 5 illustrate the formation of seal ring 40 andRedistribution Lines (RDLs) 42. The respective step is illustrated asstep 512 in the process flow shown in FIG. 25. Referring to FIG. 4,metal seed layer 39 is deposited. The respective step is illustrated asstep 508 in the process flow shown in FIG. 25. In accordance with someembodiments of the present disclosure, metal seed layer 39 includes atitanium layer and a copper layer over the titanium layer. In accordancewith alternative embodiments of the present disclosure, metal seed layer39 includes a copper layer physically contacting encapsulating material36. Metal seed layer 39 is a conformal or substantially conformal film(for example, with thickness variation smaller than about 15 percent).The formation of metal seed layer 39 may include Physical VaporDeposition (PVD), for example.

Patterned mask 41 is formed over seed layer 39. The respective step isillustrated as step 510 in the process flow shown in FIG. 25. Inaccordance with some embodiments of the present disclosure, theformation of patterned mask 41 includes dispensing and patterning aphoto resist. Next, a plating process may be performed, and a metallicmaterial such as copper or copper alloy is plated. After the platingprocess, patterned mask 41 is removed, and a flash etch is performed toremove the portions of seed layer 39 that were previously directly underpatterned mask 41. The resulting structure is shown in FIG. 5.

The remaining portions of the plated metallic material and the remainingportions of seed layer 39 are in combination referred to as RDLs 42 andseal ring 40. RDLs 42 are over encapsulating material 36. Seal ring 40penetrates through encapsulating material 36, and may extend from afirst level higher the top surfaces of package components 28 to a secondlevel lower than or level with the bottom surfaces of package components28. Furthermore, seal ring extension portions 43 are formed overencapsulating material 36.

FIG. 24 illustrates a magnified view of a portion of the structure shownin FIG. 5. Seal ring 40 (which is in opening 38A as in FIG. 3) includesa bottom portion at the bottom of opening 38A, and the bottom portionhas thickness T2. RDLs 42 include horizontal portions over encapsulatingmaterial 36 and having thickness T3. The deposited metallic material isconformal, and hence thickness T2 is close to thickness T3. For example,thickness T2 may be between about 85 percent and 95 percent of thicknessT3. Also, seal ring 40 includes an outer bottom corner 40A and an innerbottom corner 40B. The outer bottom corner may be a sharp corner with nosignificant roundness, while the inner corner 40B may be rounded, forexample, with radius R1 greater than about 50 percent of thickness T2,and ratio R1/T2 may be in the range between about 0.5 and about 1.5.

Referring back to FIG. 5, RDLs 42 include metal trace portions overencapsulating material 36 and via portions extending into openings 38B(FIG. 3), so that RDLs 42 are electrically connected to conductivefeatures 30. Although not illustrated, the portions of RDLs 42 directlyover openings 38B may have recesses due to the conformal profile of RDLs42.

Referring to FIG. 6, dielectric layer 44 is formed. The respective stepis illustrated as step 514 in the process flow shown in FIG. 25. Inaccordance with some embodiments of the present disclosure, dielectriclayer 44 is formed of a polymer such as PBO, polyimide, or the like. Inaccordance with alternative embodiments, dielectric layer 44 is formedof an inorganic material such as silicon nitride, silicon oxide, or thelike. Openings 46 are then formed, for example, through a photolithography process. Seal ring extension portions 43 and RDLs 42 areexposed to openings 46.

FIG. 24 also illustrates a magnified view of a portion of dielectriclayer 44. Due to the openings 38A as shown in FIG. 5, the top surface ofdielectric layer 44 (FIG. 24) has a recess directly over seal ring 40.The recess is directly over a portion of dielectric layer 44 extendingbetween opposite sidewall portions of seal ring 40, which sidewallportions are on opposite sidewalls of the respective opening 38A. Therecess depth D1 may be greater than about 30 percent of thickness T3,and may be in the range between about 30 percent and about 50 percent ofthickness T3.

Referring to FIG. 7, more features are formed over dielectric layer 44,which features include dielectric layers 50 and 54 and RDLs 48, 52, and56. The respective step is illustrated as step 516 in the process flowshown in FIG. 25. In accordance with some embodiments of the presentdisclosure, the formation of RDLs 48 includes depositing a metal seedlayer (not shown), forming and patterning a photo resist (not shown)over the metal seed layer, and plating a metallic material such ascopper or aluminum over the metal seed layer. The metal seed layer andthe plated material may be formed of the same material or differentmaterials. The patterned photo resist is then removed, followed byetching the portions of the seed layer previously covered by thepatterned photo resist. The materials and the formation processes ofRDLs 52 and 56 may be similar to that of RDLs 48. The materials and theformation processes of dielectric layers 50 and 54 may be similar tothat of dielectric layer 44. The details are thus not repeated herein.

Integrated Passive Device (IPD) 60 may be bonded to RDLs 56, andelectrical connectors 58 are formed in accordance with some exemplaryembodiments. The respective step is illustrated as step 518 in theprocess flow shown in FIG. 25. In accordance with some embodiments ofthe present disclosure, Under-Bump Metallurgies (UBMs) are not formed,and electrical connectors 58 are formed directly on RDLs 56. This may beachieved when the respective package is a low-cost package, and hencesome features (such as UBMs and the through-vias penetrating throughencapsulating material 36) are skipped to reduce manufacturing cost. Inaccordance with alternative embodiments of the present disclosure, UBMs(not shown) are formed between RDLs 56 and electrical connectors 58.

The formation of electrical connectors 58 may include placing solderballs on the exposed portions of RDLs 56, and then reflowing the solderballs. In accordance with alternative embodiments of the presentdisclosure, the formation of electrical connectors 58 includesperforming a plating process to form solder layers over RDLs 56, andthen reflowing the solder layers. Electrical connectors 58 may alsoinclude metal pillars, or metal pillars and solder caps on the metalpillars, which may also be formed through plating. Throughout thedescription, the structure including dielectric layer 24 and theoverlying structure in combination is referred to as package 100, whichmay be a composite wafer (and also referred to as composite wafer 100hereinafter) including a plurality of package components 28.

Next, package 100 is de-bonded from carrier 20, for example, byprojecting a UV light or a laser beam on release layer 22, so thatrelease layer 22 decomposes under the heat of the UV light or the laserbeam. The respective step is illustrated as step 520 in the process flowshown in FIG. 25. The resulting package 100 is shown in FIG. 8. Inaccordance with some embodiments of the present disclosure, in theresultant package 100, dielectric layer 24 remains as a bottom part ofpackage 100, and protects seal ring 40. Next, a singulation (die-saw)process is performed to separate composite wafer 100 into individualpackages 100′ (FIG. 9). The respective step is also illustrated as step520 in the process flow shown in FIG. 25.

FIG. 9 also illustrates the bonding of package component 320 to package100′, thus forming package 322. The respective step is illustrated asstep 522 in the process flow shown in FIG. 25. The bonding is performedthrough solder regions 58, which join RDLs 56 to metal pads 324 inpackage component 320. In accordance with some embodiments of thepresent disclosure, package component 320 includes a package substrate,an interposer, a printed circuit board, or the like.

In package 322, some portions of RDLs 48, 52, and 56 form seal ring 62in dielectric layers 44, 50, and 54, with each of the correspondingparts of RDLs 48, 52, and 56 forming a full ring proximal the peripheralof package 100′. Seal ring 62 is connected to the seal ring extensionportions 43 (which also forms a full ring) and seal ring 40 to form sealring 64. Seal ring 64 thus extends all the way from the top surface ofdielectric layer 54, which is the top dielectric layer in package 100′,to the bottom surface of encapsulating material 36. Accordingly, packagecomponents 28 are also protected from detrimental substance such asmoisture and chemicals that may penetrate through encapsulating material36 to degrade package components 28.

In package 322, encapsulating material 36 includes a first portion atthe same level as package components 28, and a second portion higherthan package components 28. The first portion and the second portion arethe portions of an integrated and continuous material, with nodistinguishable interface therebetween. Furthermore, there is nogrinding mark in the top surface of encapsulating material 36 since thefirst portion and the second portion are formed in a same process, andno planarization is performed between the formation of the first portionand the second portion.

FIGS. 10 through 21 illustrate the perspective views and cross-sectionalviews of intermediate stages in the formation of a package in accordancewith some embodiments of the present disclosure. These embodiments aresimilar to the embodiments shown in FIGS. 1 through 9, except no sealring is formed in the encapsulating material. Rather, metal pins areplaced in the encapsulating material. Unless specified otherwise, thematerials and the formation methods of the components in theseembodiments are essentially the same as the like components, which aredenoted by like reference numerals in the embodiments shown in FIGS. 1through 9. The details regarding the formation processes and thematerials of the components shown in FIGS. 10 through 21 may thus befound in the discussion of the embodiments shown in FIGS. 1 through 9.The steps shown in FIG. 10 through 21 are also illustrated schematicallyin process flow 600 as shown in FIG. 26.

Referring to FIG. 10, stencil 66 is provided. Stencil 66 may be formedof a rigid material such as a metal (stainless steel, copper, aluminum,or the like). Through-holes 68 are formed in stencil 66. The stencil 66may be attached to a vacuum head (not shown), which is configured toevacuate air in the direction shown by arrows. Metal pins 70 include pinheads 70A and pin tails 70B. It is appreciated that pin heads 70A, pintails 70B, and through-holes 68 may have circuit shapes or other shapesincluding, and not limited to, squares, hexagons, or the like. Pin heads70A have a diameter (or a lateral dimension) greater than the diameterof through-holes 68, and pin tails 70B have a diameter (or lateraldimension) smaller than the diameter of through-holes 68. Accordingly,when pin tails 70B are inserted into through-holes 68, pin heads 70A areblocked. Referring to FIG. 11B, in accordance with some embodiments ofthe present disclosure, diameter Dial of pin head 70A is in the rangebetween about 200 μm and about 250 μm, diameter Dia2 of pin tail 70B isin the range between about 150 μm and about 200 μm, and diameter Dia3 ofthrough-hole 68 is in the range between about 180 μm and about 230 μm.The total height H1 of metal pins 70 may be in the range between about200 μm and about 250 μm.

Referring to FIG. 11A, metal pins 70 are inserted into through-holes 68.The respective step is illustrated as step 602 in the process flow shownin FIG. 26. The insertion may be achieved, for example, throughpicking-and-placing. In accordance with alternative embodiments, metalpins 70 are inserted by pouring metal pins 70 over stencil 66, andvibrating stencil 66, so that tails 70B fall into through-holes 68.After pin tails 70B are inserted into through-holes 68, vacuuming isprovided, causing metal pins 70 to be secured onto stencil 66 by thevacuum. FIG. 11B illustrates a cross-sectional view of portion 71 inFIG. 11A.

Referring to FIG. 12, stencil 66 is flipped upside down along with metalpins 70 fixed thereon. Metal pins 70 are then moved to DAF 25. Thevacuum causes metal pins 70 to hold on stencil 66. In accordance withsome embodiments of the present disclosure, as shown in FIG. 12, DAF 25is adhered to dielectric layer 24, which is further formed on releasefilm 22. Release film 22 is coated on carrier 20. Carrier 20, releasefilm 22, dielectric layer 24, and DAF 25 may have a round top-viewshape, on which a plurality of identical packages may be formed.

Metal pins 70 are pressed against, and are adhered to, DAF 25. Therespective step is illustrated as step 604 in the process flow shown inFIG. 26. Next, the vacuum is released, and stencil 66 is moved away. Ina subsequent step, package components 28 are adhered to DAF 25, as shownin FIG. 13A. The respective step is illustrated as step 606 in theprocess flow shown in FIG. 26. FIG. 13A illustrates a single packagecomponent 28, while in reality, a plurality of package components 28 anda plurality of metal pins 70 may be placed on DAF 25 to form a pluralityof identical groups, with each of the groups including one or morepackage component 28 and a plurality of metal pins 70. In accordancewith some embodiments of the present disclosure, metal pins 70 andpackage components 28 have similar heights, for example, with a heightdifference smaller than about 20 percent the height of metal pins 70.FIG. 13B illustrates a cross-sectional view of the structure shown inFIG. 13A.

Next, referring to FIG. 14A, encapsulating material 36 is dispensed tocover package components 28 and metal pins 70. The respective step isillustrated as step 608 in the process flow shown in FIG. 26. Thematerial and the method of dispensing encapsulating material 36 may besimilar to what are discussed referring to FIG. 2, and hence are notrepeated herein. FIG. 14B illustrates a perspective view of thestructure shown in FIG. 14A.

FIGS. 15A and 15B illustrate a cross-sectional view and a perspectiveview, respectively, in the formation of openings 38B and 38C, throughwhich conductive features 30 and metal pins 70 are exposed. Therespective step is illustrated as step 610 in the process flow shown inFIG. 26. Encapsulating material 36 may be formed of a light-sensitivematerial, and hence openings 38B and 38C may be formed throughlight-exposure (using a photo lithography mask) and a developmentprocess.

FIG. 22 illustrates a magnified view of a portion of the structure shownin FIGS. 15A and 15B. Due to the height of metal pins 70, the topsurface of encapsulating material 36 includes a first portion directlyover metal pin 70, and a second portion encircling metal pins 70. Inaccordance with some embodiments of the present disclosure, theformation of encapsulating material 36 does not include a planarizationprocess (such as a CMP process or a mechanical grinding process).Accordingly, the top surface of the first portion of encapsulatingmaterial 36 is higher than the top surface of the second portion ofencapsulating material 36, with a smooth transition from the top surfaceof the first portion to the top surface of the second portion. Theheight difference ΔH2 between the top surfaces of the first portion andthe second portion is greater than about 2 μm, and may be in the rangebetween about 4 μm and about 5 μm. In accordance with alternativeembodiments of the present disclosure, a planarization process isperformed, and hence the top surface of encapsulating material isplanar. The first portion of encapsulating material 36 directly overmetal pin 70 may also have thickness T4 in the range between about 10 μmand about 30 μm. The spacing S1 between neighboring metal pins 70 may bein the range between about 100 μm and about 150 μm. The depth/thicknessD2 of encapsulating material 36 may be in the range between about 160 μmand about 250 μm in accordance with some exemplary embodiments.

FIG. 16 illustrates the formation of metal seed layer 39, which mayinclude a copper layer, or a titanium layer and a copper layer over thetitanium layer. The respective step is illustrated as step 612 in theprocess flow shown in FIG. 26. Patterned mask 41, which may be formed ofphoto resist, is then formed over metal seed layer 39. The respectivestep is illustrated as step 614 in the process flow shown in FIG. 26.The material and the formation process for forming patterned mask 41 maybe found referring to the discussion of FIG. 4. Next, as shown in FIG.17, a plating process is performed to plate a metallic material,followed by a removal process for removing patterned mask 41 and anetching process for removing the portions of metal seed layer 39directly underlying the removed patterned mask 41. As a result, RDLs 42and seal ring extension portions 43 are formed. The respective step isillustrated as step 616 in the process flow shown in FIG. 26. RDLs 42include first portions connected to some of metal pins 70 and secondportions connected to metal pillars 30. Seal ring portions 43 form aring encircling the region directly over package components 28. Inaccordance with some embodiments of the present disclosure, one or moreof metal pins 70 is connected to seal ring portions 43 for electricalgrounding purpose.

FIGS. 18 and 19 illustrate the formation of dielectric layers 44, 50,and 54 and RDLs 48, 52, and 56. The respective step is illustrated assteps 618 and 620 in the process flow shown in FIG. 26. The formationprocesses and the respective materials are discussed in the embodimentsreferring to FIGS. 6 and 7, and the details are not repeated herein.Seal ring 62 is formed to encircle RDLs 48, 52, and 56, and seal ring 62includes extension portions 43, which are electrically connected to oneof metal pins 70 for electrical grounding in the final package. IPD 60may be bonded to RDLs 56. The respective step is illustrated as step 622in the process flow shown in FIG. 26. Electrical connectors 58 areformed on RDLs 56. Composite wafer 100, which includes dielectric layer24 and the overlying structure, is thus formed.

In a subsequent step, composite wafer 100 is de-bonded from carrier 20,for example, by decomposing LTHC 22 through a laser beam or UV light.The respective step is illustrated as step 624 in the process flow shownin FIG. 26. The resulting composite wafer 100 is then singulated into aplurality of packages 100′, and FIG. 20 illustrates one of the resultingpackages 100′. The respective step is also illustrated as step 624 inthe process flow shown in FIG. 26. Metal pins 70 are then revealed byremoving some portions of dielectric layer 24 and DAF 25, for example,through laser drill, thus forming openings 72. By making pin heads 70Ato be larger than pin tails 70B, the process margin of the laser drillis enlarged.

FIG. 21 illustrates the bonding of package 300 to package 100′. Therespective step is illustrated as step 626 in the process flow shown inFIG. 26. The bonding is performed through solder regions 302, which joinmetal pins 70 to metal pads 304 in package 300. In accordance with someembodiments of the present disclosure, package 300 includes a packagesubstrate (not shown separately) and device die(s) (not shownseparately), which may be memory dies such as SRAM dies, DRAM dies, orthe like.

FIG. 21 also illustrates the bonding of package component 322 to package100′, thus forming Package-on-Package (PoP) structure/package 326. Thebonding is performed through solder regions 58, which join RDLs 56 tometal pads 324 in package component 320. In accordance with someembodiments of the present disclosure, package component 320 includes apackage substrate, an interposer, a printed circuit board, or the like.

In accordance with some embodiments of the present disclosure, the sealring 64 as shown in FIG. 9 and the metal pins 70 as shown in FIG. 21 areintegrated in a same package 100′. The respective formation process ofthe package is similar to the process shown in FIGS. 10 through 21,except in the step shown in FIGS. 15A and 15B, the through-openings 38A(similar to what is shown in FIG. 3) for forming seal ring 40 issimultaneously formed when openings 38B and 38C in FIGS. 15A and 15B areformed.

In above-illustrated exemplary embodiments, some exemplary processes andfeatures are discussed in accordance with some embodiments of thepresent disclosure. Other features and processes may also be included.For example, testing structures may be included to aid in theverification testing of the 3D packaging or 3DIC devices. The testingstructures may include, for example, test pads formed in aredistribution layer or on a substrate that allows the testing of the 3Dpackaging or 3DIC, the use of probes and/or probe cards, and the like.The verification testing may be performed on intermediate structures aswell as the final structure. Additionally, the structures and methodsdisclosed herein may be used in conjunction with testing methodologiesthat incorporate intermediate verification of known good dies toincrease the yield and decrease costs.

The embodiments of the present disclosure have some advantageousfeatures. By dispensing an encapsulating material to cover device diesand/or metal pins, the encapsulating material acts as both theencapsulating material and the dielectric layer covering the devicedies. The manufacturing cost is thus reduced since the otherwise twoformation processes are merged into one process. Also, the planarizationprocess that is otherwise performed on the molding material is skipped,causing the further reduction in the manufacturing cost. The seal ringmay be formed extending into the encapsulating material, resulting inthe improvement in the isolation of the device dies from detrimentalsubstances. Metal pins may be used to replace through-vias that areformed through plating, which also reduces the manufacturing cost.

In accordance with some embodiments of the present disclosure, a methodincludes encapsulating a package component in an encapsulating material,with the encapsulating material including a portion directly over thepackage component. The portion of the encapsulating material ispatterned to form an opening revealing a conductive feature in thepackage component. A redistribution line extends into the opening tocontact the conductive feature. An electrical connector is formed overand electrically coupling to the conductive feature. The method of claim1 further includes patterning a second portion of the encapsulatingmaterial to form a through-opening penetrating through the encapsulatingmaterial, wherein the through-opening extends to a level at leastcoplanar with a bottom surface of the package component; and filling thethrough-opening to form a seal ring in the encapsulating material. In anembodiment, the seal ring comprises opposite portions on oppositesidewalls of the encapsulating material, and the method furthercomprises dispensing a dielectric layer, with a portion of thedielectric layer extending between the opposite portions of the sealring. In an embodiment, the seal ring is a full ring encircling thepackage component. In an embodiment, the method further includes anadditional seal ring over the encapsulating material, wherein the sealring and the additional seal ring are interconnected to form anintegrated seal ring. In an embodiment, the method further includesencapsulating a plurality of metal pins in the encapsulating material,wherein the encapsulating material comprises second portions directlyover the metal pins, and wherein when the first portion of theencapsulating material is patterned, the second portion of theencapsulating material is simultaneously patterned to form a recessrevealing the plurality of metal pins. In an embodiment, the methodfurther includes pre-forming the plurality of metal pins; attaching theplurality of metal pins that has been formed onto an adhesive film; andattaching the package component to the adhesive film. In an embodiment,no planarization is performed on the encapsulating material, and at atime the redistribution line is formed, the first portion of theencapsulating material has a first top surface, and a second portion ofthe encapsulating material encircling the package component has a secondtop surface lower than the first top surface. In an embodiment, theencapsulating material is free from filler particles therein.

In accordance with some embodiments of the present disclosure, a methodincludes attaching a device die to a base layer; encapsulating thedevice die in an encapsulating material, wherein the encapsulatingmaterial comprises a first portion directly over the device die, and asecond portion encircling the first portion; patterning the firstportion of the encapsulating material to form a first opening revealinga conductive feature in the device die; patterning the second portion ofthe encapsulating material to form a second opening revealing the baselayer; forming a redistribution line extending into the first opening;and forming a seal ring extending into the second opening. In anembodiment, the first portion and the second portion of theencapsulating material are patterned simultaneously. In an embodiment,the encapsulating material is formed of a light-sensitive material, andthe patterning the first portion and the patterning the second portionof the encapsulating material comprise a light-exposure and adevelopment. In an embodiment, the seal ring extends from a first levelhigher than a top surface of the device die to a second level lower thana bottom surface of the device die. In an embodiment, the seal ringfully encircles the device die. In an embodiment, in a cross-sectionalview of the seal ring, the seal ring has a U-shape, and the methodfurther comprises forming a dielectric layer over the encapsulatingmaterial, with the dielectric layer extending into the U-shape.

In accordance with some embodiments of the present disclosure, a packageincludes a device die; an encapsulating material encapsulating thedevice die therein, wherein the encapsulating material comprises: afirst portion directly over the device die, wherein the first portionhas a first top surface; and a second portion encircling the device die,wherein the second portion has a second top surface lower than the firsttop surface; a seal ring in the encapsulating material; and a firstredistribution line and a second redistribution line comprising portionsover the encapsulating material, wherein the first redistribution lineand the second redistribution line are connected to the device die andthe seal ring, respectively. The package of claim 16, wherein the sealring penetrates through the encapsulating material, and extends from afirst level higher than a top surface of the device die to a secondlevel lower than a bottom surface of the device die. In an embodiment,the seal ring comprises opposite portions contacting the encapsulatingmaterial, and the package further comprises a dielectric materialextending between the opposite portions of the seal ring. In anembodiment, the first surface is continuously and smoothly connected tothe second surface. In an embodiment, the seal ring is a full ringwithout break in a top view of the package.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A package comprising: a device die; anencapsulating material encapsulating the device die therein, wherein theencapsulating material comprises: a first portion directly over thedevice die, wherein the first portion has a first top surface; and asecond portion encircling the device die, wherein the second portion hasa second top surface lower than the first top surface; a seal ring inthe encapsulating material; and a first redistribution line and a secondredistribution line comprising portions over the encapsulating material,wherein the first redistribution line and the second redistribution lineare connected to the device die and the seal ring, respectively.
 2. Thepackage of claim 1, wherein the seal ring penetrates through theencapsulating material, and extends from a first level higher than a topsurface of the device die to a second level no higher than a bottomsurface of the device die.
 3. The package of claim 2, wherein the sealring comprises a first vertical portion and a second vertical portioncontacting the encapsulating material, and the package further comprisesa dielectric material comprising a lower portion extending between thefirst vertical portion and the second vertical portion of the seal ring.4. The package of claim 3, wherein the dielectric material furthercomprises an additional portion overlapping the encapsulating material.5. The package of claim 3, wherein the seal ring comprises a portiondirectly underlying the lower portion of the dielectric material.
 6. Thepackage of claim 1, wherein the first top surface is continuously andsmoothly connected to the second top surface.
 7. The package of claim 1,wherein the seal ring is a full ring without break in a top view of thepackage, and the seal ring encircles the device die.
 8. The package ofclaim 1 further comprising a dielectric layer underlying and in contactwith both of the encapsulating material and the seal ring.
 9. A packagecomprising: a first dielectric layer; a molding compound over the firstdielectric layer; a conductive ring over the first dielectric layer,wherein the conductive ring encircles a portion of the molding compound;and a second dielectric layer comprising: a first portion over themolding compound; and a second portion extending into the conductivering.
 10. The package of claim 9, wherein the conductive ring penetratesthrough the molding compound.
 11. The package of claim 9 furthercomprising a redistribution line over and contacting the moldingcompound, wherein the first portion of the second dielectric layerfurther overlaps the redistribution line.
 12. The package of claim 11further comprising a device die encapsulated in the molding compound,wherein the redistribution line comprises a line portion, and a viaportion underlying and connected to the via portion, and wherein the viaportion penetrates through a portion of the molding compound to contactthe device die.
 13. The package of claim 9, wherein the second portionof the second dielectric layer comprises a curved top surface.
 14. Thepackage of claim 9, wherein the first dielectric layer is in physicalcontact with both of the molding compound and the conductive ring. 15.The package of claim 9, wherein the conductive ring comprises a U-shapedstructure comprising: two vertical portions in contact with oppositesidewalls of the second portion of the second dielectric layer; and ahorizontal portion overlapped by and contacting the second portion ofthe second dielectric layer.
 16. A package comprising: a device diecomprising a conductive pad; a molding compound encapsulating the devicedie therein; and a plurality of conductive features comprising: a firstportion over the molding compound; a second portion penetrating throughthe molding compound; and a third portion extending into the moldingcompound to contact the conductive pad of the device die.
 17. Thepackage of claim 16, wherein the second portion of the plurality ofconductive features extends from a top surface level to a bottom surfacelevel of the device die.
 18. The package of claim 16, wherein the secondportion of the plurality of conductive features has a U-shapedstructure, and the package further comprises a dielectric layerextending into the U-shape structure.
 19. The package of claim 18,wherein the U-shaped structure has a bottom portion and two verticalportions connected to opposite ends of the bottom portion, and thepackage further comprises a polymer extending into the U-shapedstructure.
 20. The package of claim 16, wherein the second portion ofthe plurality of conductive features forms a ring encircling the devicedie.